J. Plant Prot. and Path., Mansoura Univ., Vol. 10 (1): 53 - 56 , 2019 Biological Parameters of the Conical Snail Cochlicella acuta (MÜLLER, 1774) (Gastropoda: Cochlicellidae) under Laboratory Conditions Abd El-All, E.M. 1 and Olfat E. Arafa 2* 1Plant Protection Department, Faculty of Agriculture, Zagazig University, Egypt. 2Plant Protection Research Institute, Agricultural Research Center, Dokki, Egypt. *Corresponding author : +201018434289 E.mail address : [email protected] ABSTRACT Biological parameters like as mating, pre-oviposition, oviposition, post-oviposition, and generation periods as well as growth rate of the pointed or conical snail Cochlicella acuta (Müller, 1774) (Gastropoda: Cochlicellidae )were studied in the Plant Protection Department, Faculty of Agriculture, Zagazig University under laboratory conditions. In 2017/2018,samples of pointed or conical snails of date palm were collected during its reproductive and activity season from highly infested palm tree orchards at Abo-Nagii farm, El- Kassassein, Ismailia governorate. The temperature and RH% values ranged from 19 to 28 oC and 48 to 61, respectively. Snails immediately transported back to the laboratory where they were identified to species and kept in 1000 cc boxes "plastic containers" with tight fitting perforated covers , provided with fresh lettuce leaves (Lactuca sativa ) as a source of food reared and ovipostion site. Plastic containers were staked side by side with moist soil. The fresh lettuce leaves were checked daily and replaced with fresh one. The laboratory observations revealed that in spite of this species is hermaphrodite, the cross mating was essential for ovipostion as unmated ones did not lay any egg. Mating occurs when snail individuals reach their sexual maturity as calculated from adulthood until mating. Besides large adults produced more eggs than small ones over the whole breeding season; this period was 95 ± 28.4 days in average. Pre- oviposition period (from mating till laying first egg) lasted for an average of 17.3 ± 6.1 days. Oviposition period (from laying first egg till last one) averaged 84.3 ± 23.6 days during which snail individual deposited a total of 110 ± 59.5 eggs. Post-oviposition period (from last laid egg till mortality) was 140 ± 74.3 days. The generation period (from egg to egg) of this species extended to an average of 275.3 ± 32.1 day Keywords : Cochlicella acuta - Sexual maturity – Oviposition – Generation period – Growth rates. INTRODUCTION The snails were kept in three 1000 cc (15 x 10 x 11 cm) boxes or containers filled with moist soil to eight Terrestrial gastropods play an important role in centimeters deep and were fed on fresh lettuce leaves nutrient cycling within terrestrial ecosystems (Dallinger et (Lactuca sativa ) as a source of food reared and ovipostion al., 2001) and these animals often serve as prey or host for site. a variety of animals (Scheifler et al ., 2002).On the other The plastic boxes were covered with muslin cloth hand, some gastropods, including conical snail Cochlicella fixed with rubber bands to prevent the individuals from acuta (Müller,1774) (Gastropoda: Cochlicellidae ), our escaping. Boxes were examined daily. Fresh lettuce leaves study animal, is regarded as a pest of many crops (Barker, and moisture (drops of water) were supplied as required, 2001). and the soil was searched for egg clutches. The native of Cochlicella acuta is coastal areas of All egg clutches were removed and placed in the Mediterranean and Western Europe (Lewis, 1977; prepared pots (13x10 cm) with moist soil and then Kerney and Cameron, 1979). But in 1986, Baker stated this observed twice daily till hatching to determine the species in south eastern and south Western Australia as incubation period and hatchability. New hatched snails agricultural pest, that species aestivate on ears and stalks of (juveniles) were placed solitary in plastic cups (15 x13cm) cereal plants. In addition, C. acuta contaminate grains with moist soil and fresh lettuce leaves. during harvest. In the field, Baker, 1989 mentioned that C. The cups were covered to avoid escaping of snails, acuta caused insignificant damage to these plants and were examined daily, where fresh lettuce and moisture Recently land snails had become one of economic were added as required throughout the life span. serious pests in different governorates in Egypt. It is Pairs of similar weight and shell diameter of C. causing serious yield reduction of infested filed crops and acuta snails were put in prepared pots (15 x 13cm) and fruits (Kassab and Daoud 1964 & Nakhla and Tadros, observed several times daily till mating to determine the 1995). C. acuta snail is considered one of the most periods of sexual maturity and copulation. abundant mollusc pest causing damage to palm trees, citrus After that, individuals of every pair were separated orchards and ornamental plants. and each individual was placed singly in the similar pot to The biology of this pest has been little studied and determine the pre-oviposition period, oviposition period, restricted to non agricultural habitats. Therefore, the number of egg clutches per individual, clutch size and present study was intended to determine several biological post-oviposition period. aspects of the life history (e.g. mating, life cycle, Juveniles were weighed using a digital balance, and oviposition as well as growth parameters) of C. acuta shell diameter was measured using a caliper. This was under laboratory conditions. done monthly from hatching time (zero time) till maturity MATERIALS AND METHODS (according to lips growth). The shell volume was calculated following Baur and Raboud (1988): Hundred adult individuals of C. acuta were hand Shell volume = (width) 2 x height / 2 picked from nurseries in Abo-Nagii farm, El-Kassassein, The growth rate was calculated monthly according Ismailia Governorate, Egypt, during its active period in to the formula: November 2017 on date palm trees. Abd El-All, E . M. and Olfat E. Arafa WF - WI Data were subjected to analysis of variance Growth rate = ×100 WF (ANOVA) suing MSTAT VERISION 4(1987). Where WI and WF are the initial and final weights of snails during a period RESULTS AND DISCUSSION of month. Also, the rate of change in diameter was calculated 1- Duration of different stages of Cochlicella acuta using the formula: reared on lettuce under laboratory conditions: DF - DI Data in Table (1) showed the different stages of Rate of change in diameter = ×100 DF Cochlicella acuta under reared on lettuce under laboratory Where conditions. The optimum temperature and relative DI and DF are the initial and final shell diameter of snails during a humidity, individuals reached their adulthood according to period of one month. lip signs and mating. The rate of change in shell height was calculated as: In C. acuta mating occurred when individuals HF - HI Rate of change in height = ×100 reached to sexual maturity in about 95.7 ±28.4 days (N= HF 14) after adulthood was achieved. Mating happened in day Where time between 9.20 am to 4.30 pm, during its reproductive HI and HF are the initial and final shell height of snails during a season from November till the end of February and two period of month. days in beginning of March). Also, the following formula was applied to Cross mating is essential to lay eggs, and as calculate the rate of change in shell volume. expected, during copulation two individuals faced each VF - VI Rate of change in volume = ×100 other and attached together strongly from the fleshy parts VF with a thick layer of mucus for an average period of Where VI and VF are the initial and final shell volume of snails for a period 112.5±31.2 minutes (N= 10 pairs) and separated within an of month. average period of 13.0 ± 3.5 minutes. Table 1. Duration of different stages of Cochlicella acuta reared on lettuce under laboratory conditions. Period in Days of the Following Parameters Type of Life Sexual Pre- Post- Life Items Incubation Juveniles Oviposition Generation cycle maturity oviposition oviposition span Average 12.7 245.9 258.6 95.7 16.9 84.3 123.7 542.5 275.3 ± SD ±1.7 ±26.5 ±28.2 ±28.4 ±6.8 ±23.6 ± 63.4 ±114.3 ±32.1 Temperature 21.0 24.5 24.0 27.0 22.7 18.8 26.2 24.8 23.3 ºC ±0.4 ±4.5 ±5.6 ±4.1 ±2.1 ±1.6 ±4.6 ±4.5 ±3.9 49.4 60.1 60.0 57.0 61.5 60.4 60.6 60.5 59.1 R.H.% ± 6.8 ±6.9 ±5.8 ±7.7 ±7.6 ±6.5 ±6.1 ±5.8 ±7.1 *Each value is a mean of tested Cochlicella acuta snail pairs . Regarding the ovipostion period, the both mated dimensions reached 9.5 ± 1.4 mm for height, 4.3 ± 0.6 mm individual of C. acuta or only one deposited eggs and pre- for width and weighted 0.06 ± 0.012 g (N = 30). oviposition period averaging 16.9 ± 6.8 days before Data in Table 2 assessed the life span of C. acuta depositing eggs. Whereas, oviposition period averaged during actively season. The duration of C. acuta life cycle 84.3± 23.6 days and number of average deposited clutches from egg to adulthood (incubation period plusjuveniles) per snail was 12.8 ± 5.4. In addition, the period between averaged 258.6 ± 28.2 days. Mating influenced life span of deposit two clutches and size of clutch were 6.2 ± 1.3days this species (from egg till mortality). As shown in the and 6.1, respectively. On the other hand, the white egg Table 2, unmated C. acuta snails have long life span as diameter ranged from 1.1 to 1.4mmwith smooth surface, compared to mated ones.